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hot-water circulation problems

We have a hot-water-baseboard heating system that supplies our household hot water as well. About a year ago, the hot water in the shower became unavailable unless we concurrently ran the hot water in the washing machine or sink (same room). Eventually, we found that we could stop running the secondary hot water source once the shower was running well. When we turned off the secondary source, the shower ran full force. Suddenly, even this trick doesn't work. If we turn the hot water handle 1/3 on, we get a trickle of hot water. If we open 100%, we get none. This is a hot-water only problem. Cold water runs fine. Can anyone help?

Re: hot-water circulation problems

What they said but I'll add;

Try taking it apart and cleaning it first.

We once had a customer with a similar problem, no hot water at the second floor shower. Seems a roofing type rock got all the way through the house plumbing, up to the second floor and had lodged into the hot water cartridge. It would rock back and forth allowing small amounts of water to flow if you were lucky.

Re: hot-water circulation problems

I will take the hot-water handle apart tonight and see what I can find to "clean".

I googled the cartridge to see if I could find a diagram, but everything was the single-handle control for the faucet. We don't have that. Our bath was put in about 1964, and it is two faucet handles (hot and cold) and the spigot with a pull-up knob to redirect water to the shower head.

Why wasn't it fixed a year ago? Because I discovered the work-around of turning on the hot water in the sink to get the shower going, and I was inundated with childcare and eldercare.

Re: hot-water circulation problems

This also could be caused by a TEMPERING VALVE that's become clogged.

A tempering valve/mixing valve, usually situated close to the boiler, controls the temperature & amount of HW mixed with cold water that is sent to the shower & the tub faucet so that it doesn't scald the bather; consult the site below for variations of what they look like & see if you can find one on the HW line that goes to the tub/shower; try twisting the tempering valve knob back & forth, open & closed to see if you can loosen things up & get a better water flow to the tub/shower---the older TVs/MVs usually have a black knob.

Try to trace your domestic hot water line (DHW) from where it comes out of the boiler----this is known as a "tankless coil" & is usually a round black 6" circular black plate embedded on the top front of the boiler, with a copper tube going in, and one coming out to the faucets that service the sinks, shower, etc.

Re: hot-water circulation problems

Two questions on this issue:
before changing cartridge, do you need to shut off water supply?
does changing the cartridge affect the force of the water?
(our hot water comes out a little slower and drips some out of the water spout)
Thanks